Volatile organic liquids of increased electrical conductivity



3,012,?59 VGLATEE QRGANEC LKQUHDS F 1N CREASED- ELECTRECAL CQNDUiiTlVlTY Johan Leonard van der Minne and Pieter Hendrik Jan Hermanie, Amsterdam, Netherlands, assignors to Shell (iii Qompany, a corporation of Delaware No Drawing. Filed Nov. 15, 1956, Ser. No. 622,500 Ilairns priority, application Netherlands Dec. 30, 1952 6 (Iiaims. (6i. 252-153) The present invention relates to novel organic liquid compositions, and particularly to volatile organic liquids of increased electrical conductivity.

Volatile organic liquids have long been essential commodities in our present industrial economy. Indeed, most of the many familiar industrial achievements of today would have been impossible without them. Volatile organic solvents are extensively used in chemical processes, such as in extraction and crystallization; in the manufacture of paints and other coatings, plastics, inks, linoleum, insecticides, adhesives, paper, dyes, pharmaceuticals and many other natural and synthetic chemical products; and in cleaning operations of all kinds, such as dry cleaning of fabrics, degreasing of metals and cleaning of machinery and tools. There is virtually no part of present day industry in which it is not desirable to use these solvents for one purpose or another. Additionally, volatile organic liquid fuels, for example, gasoline, are so extensively used that they now supply a very large proportion of the total energy consumption of the world.

The inflammability of these volatile liquids has been a serious problem. in some cases the danger has been minimized by confining them in vessels, pipes, etc., thus precluding any contact with the atmosphere. However, in most cases, and particularly in cleaning operations and other batch processes, it is not possible to provide this kind of protection continuously because of the nature of the process. For example, in dry cleaning it is necessary to agitate fabrics and solvents together in atmospheric tanks and in degreasing processes it is also necessary to expose the inflammable liquid to the atmosphere. Similarly, while gasoline can usually be confined to the exclusion of air during its manufacture, it is, of course, inevitable that it will come into contact with air during refueling of the vehicles in which it is to be used.

An aggravation of this hazard of inflammability occurs when the volatile liquid is agitated. It is a well-known and universally feared propensity of these liquids to'develop static electrical charges under such conditions, the discharge of which is often accompanied by sparks which may ignite the liquid. This danger can sometimes be controlled by grounding the metallic container of the liquid. For example, it is the universal custom to use a grounding chain on a gasoline transport truck, and to provide a tight grounding connection between the truck and the loading pipe or receiving vessel when the gasoline is either loaded at the refinery or delivered. These precautions, however, are not inevitably effective. There always remains the possibility of a faulty ground connection or an inadvertent lack of a ground connection, and in the case of cleaning operations, particularly dry cleaning or the cleaning of any material which does not conduct electricity, or in many centrifuging operations in which a solid is separated from a liquid, it is usually not possible to ground the entire work effectively.

Another problem which is often encountered in processes involving volatile organic liquids is that it is frequently necessary to measure the level of such liquids in vessels under pressure. Heretofore, it has been necessary to employ such means as a mechanical float extending into the pressure vessel through a packing gland. This Patented Dec. 12, 1981 is'a highly objectionable method because of mechanical difficulties with the packing gland which frequently lead to leakage and/or high maintenance costs. However, in the case of liquids which can conduct electricity to some extent, it is possible to employ an electrode type of liquid level measuring device whereby an electrical circuit is completed through the liquid itself as the level of the liquid reaches a certain height. This type of liquid level measuring device is advantageous also in open vessels or in closed vessels not under pressure because it eliminates the float, Which is mechanically vulnerable and is often in the Way, especially during batch operations such as fabric cleaning and the like. Thus, while increasing the conductivity of carbon tetrachloride, for example, would not be useful from the standpoint of reducing the likelihood of its catching fire from spark discharge of static electricity, it would be highly useful and advantageous by making possible the use of an electrode type of liquid level measuring device.

It is known that dangers in handling volatile inflammable organic liquids can be alleviated if the electrical conductivity of the liquid is raised, thus enabling static electrical charges to be dissipated through the liquid and to flow to a ground before accumulating to the extent necessary to cause a spark discharge. A number of additives have been proposed to accomplish this. For example, the Flett US. Patents 2,290,870; 2,326,772; 2,327,- 182; and 2,327,183, teach that the electrical conductivity of volatile organic solvents used in dry cleaning is increased by the addition of a small quantity of a salt, such as the ammonium, alkali metal, or alkaline earth metal salt of certain organic sulfonic acids or acid sulfuric acid esters. It has also been proposed to increase the electrical conductivity of dry cleaning solvents by the addition of a polyvalent metal soap, such as magnesium oleate (U.S. 2,503,744), or a substituted ammonium salt of a fatty acid or a resin acid (British Patent No. 356,717). Such additives as heretofore known, however, have had the disadvantage that it has been ordinarily necessary to incur, porate into the liquid relatively large quantities in order to increase the conductivity of the liquid to the required degree. It is obvious that as the concentration increases, the proportional and therefore the quantitative loss of the additive is also increased in such processes as revivifying cleaners naphtha, re-distilling gasoline or] other solvents used in degreasing operations, separation of the solvent from extract in an extraction operation or solid from liquid in a centrifugal process, and similar processes. Furthermore, it is usually desirable to minimize the concentration of additives such as these in order to avoid such deleterious effects as, for example, contamination of products in extraction processes and the like, residual odors in dry cleaned fabrics, and deposits and plugging in fuel systems, such as in carburetor jets and intake valves. In the case of fuels, it is of course desirable to minimize the concentration of the additive for the additional reason that it is not recovable to any degree.

It is therefore a principal object of the. present invention to provide improved volatile organic liquid compositions which are safer, more economical and more convenient to use. A further object of the invention is to provide an economical method for minimizing the propensities of such liquids for the accumulation of static electrical charges. Another object of the invention is to provide volatile organic liquid compositions of increased electrical conductivity. Still another object of the invention is to provide volatile liquid organic compositions the electrical conductivity of which has been effectively increased by the addition of less than the usual quantities of conductivity additives.

It has now been discovered that by the proper selection of combinations of certain additives the electrical conductivity of volatile organic liquids can be increased to a given extent by the incorporation of a smaller total concentration of additives than heretofore possible. Similarly, by the selection of combinations of additives according to the present invention a given total concentration of additives will result in higher conductivities of such liquids than heretofore possible.

According to the invention the conductivity of volatile organic liquids is increased by dissolving therein two additives, the first of which (hereinafter referred to as Additive A) is a polyvalent metal organic salt having a molecular weight of at least 200, and the second of which (hereinafter referred to as Additive B) is an oxygenated (i.e., oxygen-containing) organic compound having a molecular weight of at least 200, and the product of the molecular weight of which times the specific conductivity (in the units, ohm-' cm.- of which in benzene, at a concentration of one gram per liter, is at least l 10- and which furthermore contains no ion common to Additive A, namely, the organic polyvalent metal salt.

These particular combinations of additives have the surprising effect of increasing the conductivity of a volatile organic liquid to values far greater than the sum of the conductivities of solutions of the individual additives alone at the same concentrations and the same temperature. In some cases, the conductivity of the solution containing the combination of additives is over 100 times the sum of the conductivities of solutions containing the individual additives. For example, a solution of 1.4 1i)- gram mole of chromium diisopropyl salicylate per liter in benzene has a specific conductivity (0,,) of 1l 10- ohmcm.- and a solution of 23x10" gram mole of sodium dioctyl sulfosuccinate (i.e., the sodium salt of the sulfonated dioctyl ester of succinic acid) per liter in benzene has a specific conductivity (1 of 12 l0- ohm" cmr The sum of the conductivities affected by the two aforesaid additives separately in the concentrations stated (GA-H13), thus amounts to 23X l()" ohm cm.- If, however, 1.4x gram mole of chromium diisopropyl salicylate (as Additive A) and 2.3 l0- gram mole of sodium dioctyl sulfo succinate (as Additive B) are dissolved simultaneously in one liter of benzene, the specific conductivity of the solution thus obtained (O'A+B) amounts to 3800 l0- ohm -cm. The ratio of the actual conductivity of the solution in which the two components are present in said concentrations, to the conductivity which is calcu lated as the sum of the conductivities brought about by the two components separately therefore, amounts to 3800:23=165.

The organic liquid into which the combination of substances for increasing electrical conductivity is incorporated is one which has a dielectric constant at 20, C. of less than 9, and preferably less than 7, and substantially all of which (i.e., at least 90 mol percent) consists of a compound or mixture of compounds having no more than 12 carbon atoms per molecule and preferably no more than 10 carbon atoms per molecule. The preferred class of such volatile organic liquids consists of hydrocarbons; however, also suitable are halogenated hydrocarbons, preferably containing up to 4 halogen atoms, preferably bromine and/ or chlorine, per molecule, nitrated hydrocarbons, preferably those containing no more than one nitrogen atom per molecule, and hydrocarbyl ethers Preferably containing no more than 2 atoms of oxygen per molecule, and especially such volatile organic liquids which are inflammable. As a matter of fact, and fortuitously, the invention is of particular importance for the very volatile and inflammable hydrocarbon liquids, such .4 as those having flash points (ASTM Test Method D-56) below about F., since with these liquids the danger of ignition or explosion occurring as a result of electrical charges is particularly great.

Examples of organic liquids suitable for the purpose of this invention are aliphatic hydrocarbons or mixtures thereof, such as hexane, heptane, etc.; aromatic hydrocarbons or mixtures thereof such as benzene, toluene, the xylenes; cyclo-aliphatic hydrocarbons, for example decalin and cyclohexane; mixtures of the various types (aliphatic, cycloaliphatic and aromatic) of hydrocarbons; halogenated hydrocarbons, for instance chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, and ethers, for example diethyl ether and dioxane. Liquid mixtures of which one of the components as such possesses a dielectric constant of 9 or more are also suitable, provided the dielectric constant of the whole mixture is less than 9. An example of such a mixture is a mixture of benzene with a minor proportion of nitrobenzene. The invention is applicable and beneficial particularly in the case of all of the volatile liquid petroleum products substantially all of which consist of hydrocarbons having no more than 12 carbon atoms per molecule, for example, gasoline, VM and P naphtha, cleaners naphtha, lighter fluid, mineral spirits, rubber solvent, lacquer diluent, and special low boiling range solvents of all kinds such as direct cuts of xylenes and non-aromatics boiling in or near the xylene range, or similar toluene or benzene cuts, or iso-pentane cuts.

Additive A, the polyvalent metal salt, may be derived from various types of organic acids. The term organic acid as used herein refers to any organic compound containing one or more ionizable hydrogen atoms, the ionization constant of one of which is at least about 10- and preferably at least about 10 Thus, the term includes phenols, naphthols, sulfonic acids, carboxylic acids and the thio analogs thereof. Substituted or unsubstituted aliphatic, cyclo-aliphatic and aromatic mono or polycarboxylic acids are suitable. Also suitable are monovalent or polyvalent, substituted or unsubstituted phenols, naphthols and sulfonic acids. The preferred class of compounds suitable as Additive A consists of the salts of aliphatic and aromatic carboxylic and sulfonic acids.

In general, a salt of one of the above-defined organic acids and any polyvalent metal is suitable as long as the molecular weight of the salt is at least 200 and preferably not more than about 1500. However, it is preferred that the polyvalent metal have a valence of either 2 or 3 in the salt. Polyvalent metals having atomic num' bers of from 12 through 29 are particularly effective. Examples of such suitable polyvalent metals are the alkaline earth metals (calcium, magnesium, strontium, barium), copper, zinc, cadmium, aluminum, lead, chromium, molybdenum, manganese, iron, cobalt and nickel. Of these the alkaline earth metals are especially preferred, but those metals having a valence of from 2 through 3 as well as an atomic number of from 12 through 29 are exceptionally effective.

More specific examples of Additive A are the salts of the higher fatty acids, for instance calcium oleate and magnesium oleate; the salts of substituted higher fatty acids, for example calcium phenyl stearate; the salts of alkyl-substituted aromatic carboxylic acids, for example of alkylated salicylic acids, such as diisopropyl salicylic acid or salicylic acids substituted with longer alkyl groups, for example alkyl groups with 14 to 18 carbon atoms; the salts of the sulfonated dialkyl esters of aliphatic dicarboxylic acids, for example, the sulfonated dioctyl ester of succinic acid; the salts of petroleum sulfonic acids,

and the salts of substituted phenol-formaldehyde condon Sation products, such as the calcium salt of an octyl' phenol formaldehyde condensation product.

Additive A is added to the organic liquid in quantities which may vary within relatively wide limits. In general a satisfactory increase of the electrical conductivity of the organic liquid is obtained if the particular Additive A is dissolved in the organic liquid (in combination with Additive B) in a concentration of less than 0.001 gram mole per liter. In most cases concentrations of in general only small quantities of Additive B too, need be dissolved therein to obtain the desired increase in the specific conductivity. In most cases concentrations of Additive B of from about 1x10 to about 1 1O- gram the polyvalent metal salt lying between 1x10 and mole per liter are suificient. If desired, however, larger 1X10- gram mole per liter will be sumcient. However, quantities of Additive B can be used, for example 0.001 considerably larger concentrations, for instance of 0.01 or even 0.01 gram mole per liter, and for many purposesgram mole per liter, may also be used, if the salt is sufconcentrations as low as 1 10 are advantageous. ficiently soluble in the organic liquid, and for many pur- To illustrate the strikin and surprising effect of the adposes concentrations as low as 1X l() are advantageous. ditive combinations of the present invention, additional Additive B can also be a polyvalent metal organic salt, examples are given in the following table. It is to be but in this case Additive B must diifer from Additive A emphasized that these examples are by no means exhauswith respect to both the cation and the anion. Additive B tive and that they are not to be construed as limiting the may be an alkali metal salt or an ammonium salt or a salt broad scope of the invention. It will be noted that the of an organic base, for instance a quaternary ammonium quantitative advantage of these examples of compositions salt, a quaternary phosplioniuni salt, or ternary sulfonium of the present invention is directly measurable as the ratio salt. Additive B can moreover, be an organic acid such 6A B as defined above or any other organic compound, but it must have, in any case, a molecular weight of at least 200, +073 e p y t least 300 and preferably not over a t which is the ratio of the conductivity of the compositions 10,000, especially not over about 1500, and must satisfy containing Additive A and Additive B in combination the requirement that the product of the molecular weight (O'A+B) to the sum of the conductivities of separate 1 of the substance and the specific conductivity, ohm {io s f Additiv A and Additive B individually (o' +a' cmf of a solution of 1 gram of the substance in 1 liter of all at the same temperature and concentrafions. If the benzene is at least 1 10- P. Further examples of suitable value of this ratio were 1, no combination efiect would compounds Additive B a 511501165, m d s, be indicated but values greater than 1 indicate that a polyalkylene oxides, phenolformaldehyde condensation combination effect was obtained and the magnitude thereproducts, alcohols, ethers, esters, om'dized mineral oils, of. Additive combinations exhibiting a value of this ratio phosphatides and asphaltenes. of at least about 20 and particularly at least about are Just as only small quantities of Additive A, the polypreferred.

Table Concentrations, gram Item Organic liquid base and its moles/liter a A No. Additive A Additive B dielectric constant, e, at 20 C. A-hm Add. A Add. B

1 Calcium diisopropyl salicylate Tetraisoamyl ammonium picrate. Benzene (e=2.28) 2X10-4 2 10- 01 2 do 0 2X10- 2 10- 24 3 Ferric diisopropyl salicy 1. 4 l0 2X10-6 16 4-, Aluminum diisopropylsalic at 1.5X10-2 2X1O-4 83 5. Ohromic diisopropyl salicylate 1. 4X10-4 2Xl0' 8 Ma ncsium dlisopropvl salicyla. 2.1)(10 2X10! 9 7 2X10-4 2X10-5 43 1. 3X10- 2 10- 43 1. 6 i0 2X10- 7 d 1. 6X10- 2Xi0- 6 11 Magnesium olea 1.7)(10- 2X10-4 26 Calcium petrole 1.2 10- 2X10 6 (mol. wt.888). l3 Magnesium petroleum sulfate d0 (1o 1.2)(10' 2x10 10 (mol. wt.872). 14"--- Calcium compound of mixture of do.- do 1. 6X10-* 2X10- 87 alkyl salicylates with 1-2 Cit-Cit chains.

Picric acid do 2 i0 4.4 10- s7 Tributyl ammonium picrate 2X10-4 2.4 l0- 32 Sodium dioctyl sulphosueoiuate 2X10-3 2.2X10-3 4 Chrorrtiium dioctyl sulphosue- 1X103 1 10- 16 C1118. e Octyl phenohiormaldehyde con- 2 l0- 1 g./litcr 22 densation product Polyethylene glycol alkyl aryl 2 1O-4 1. 5X10-5 13 ether (m.w. 046) Polyethylene glycol alkyl aryl 1X10-3 1.l3 10- 31 other (m.W. 8S8) Dodecyl phenyl polyethylene gly- 2X104 1. l 10- 10 001 other (m.w. 702) Polyoxyetliylene derivative of sor- 2X10-4 1.35 10- 51 bitan monolaurate (m.w. 735) Orddation resin 1 2X10 1.43 10' 10 Asphaltenes (est. m.w. 10,000). 2 10- 1X10 40 Lecithine 2 10 1.3)(10- 16 Stearic acid ester of polyethylene 2X10-4 1. 9X105 33 glycol (m.w. 518). Polyethylene oxide 1X103 9. 1X10-5 Duponts additive PL 164- 1X10 3 i. 6 i0 170 Sodium dioctyl sulf0sucoinate 1. 4X10-5 2.3 10- 1G5 Lithium dioctyl suliosucsinate 1. 4 l0 2. 3 10 33 Ammonium dioctylsulfosuccinata. 1.4)(10- 2.3)(10- 19 33 ,do Sodium petroleum suliouate. 1. 4X10"4 2.2) 1O- 29 34 Chromium dioctylsu josucciuaten Aluminum diisopropyl salicylate 7.5)(10- 1.5)(10- 49 35 Calcium compound of mixture of Lecithins 1X10-2 1. 3 10- 12 monoalkyl and dialkyl salicylates, the alkyl group of which contains 14 18 carbon atoms. 36 Chromium diisopropyl salicylate. Sodium diotyl suliosuccinate 1.4t l0- 2. 3X10 3 37 lo. Lithium dioctyl sulfosuccinate. 170, 38 do Ammoniumdioctylsulfosuccinate. 8

Table-Continued Concentrations. gram Item Additive A Additive B Organic liquid base and lts moles/liter No. dielectric constant, c, at 20 C.

a1s+zrn Add. A Add. B

39"... Calcium diisopropyl salioylate Tetraisoamyl ammonium picrate Dioxane (e=2.22 (at 25C 1X10 4 10- 38 40 do.-- n Trlig hmgethylene (=3.42 (at 1x10 1x10- 17 Diethyl other (e=4.33) 1 (l0- 1X10 11 Benzene 100% volume, nitroben- 1X10- 1 10-' 49 zene 0% volume (e=2.28). Benzene 98.82% volume, nltroben- IXIO- lXlO- 40 zone 1.18% volume (e=2.50). Benzene 97.47% volume, nitroben- 1X10' 1X10- 34 zone 2.53% volume (e=2.75). Benzene 96.15% volume, nitroben- 1Xl0- 1X10 23 zone 3.85% volume (e=3.00). Benzene 91.08% volume, nitroben- 1X10" 1X10" 8. 2

zene 8.92% volume (e=4.00).

1 Obtained by heating at 200 C. for 77 hours an acid treated lubricating o co. per minute, after which oxidation was continued for a further 40 hours at 25 components not dissolved in pentane were removed by filtration, the penta dation resin) adsorbed by this iullers earth were obtained by dissolving in It will be noted that the above compositions are of widely varying nature and yet are all within the broad definition of the invention. The Additives A are all polyvalent metal salts of organic acids (as defined hereinbefore) and have molecular weights of at least 200; the Additives B are all organic compounds having molecular weights of at least 200 and the products of the molecular weights of which times the specific conductivities (in the units, ohm" cm.- of which in benzene, at a concentration of one gram per liter are at least 1 X these Additivcs B furthermore containing no ion common to the specific Additive A of the same composition; and the organic liquids in which the additives are incorporated have from 1 through 15 carbon atoms on the average, and have dielectric constants at C. less than 9. In order to ex emplify the importance of the above limitations, the following examples are given inwhich a substantial combination effect was not obtained. In each case, the aforementioned requirements are not met in a specified respect: The item numbers given after certain of the following examples, indicating efiective compositions with which these ineffective examples are to be compared, are those numbers appearing in the left-hand column of the foregoing table.

a. Benzene solutions of isoamyl ammonium picrate (1 through 12) or of ammonium diisopropyl salicylate (13) as Additive B with the following organic compounds which, however, are not polyvalent metal salts:

(12) Sodium petroleum sulfonate (compare with items 12 and 13 of the table) (13) Sodium dioctyl sulfosuccinate b. Benzene solutions of calcium diisopropyl salicylate as Additive A, with the following organic compounds, the molecular weights of which are over 200, but the product of the molecular weights of which times the specific conductivity (in the units, ohmcm.- of which in benzene, at a concentration of one gram per liter, are, respectively, less than 1 X 10- i1 distillate while air was conducted through the distillate at a rate of 250 0 C. The oxidation product thus obtained was dissolved in pentane, the ne solution was trested with fuller's earth and the oxidation products (oxia mixture of ethanol and benzene.

(1) Polyethylene glycol alkyl aryl ether (molecular weight=404) (2) Hydroqninone dioctyl ether (molecular weight=334) c. Benzene solutions of two compounds which meet all of the requirements of Additive A and Additive B, respectively, except that one ion is common to both:

(1) Calcium diisopropyl salicylate (A) and calcium petroleum sulfonate (B) (compare with item 33 of the table) (2) Chromium diisopropyl salicylate (A) and ammonium diisopropyl salicylatc (B) (compare with items 5 and 38 of the table) (3) Calcium diisopropyl salicylate (A) and diisopropyl salicylic acid (B) (compare with item 15 of the table) (4) Chromium dioctyl sulfosuccinate (A) and sodium dioctyl sulfosuccinate (B) (compare with item 36 of the table) (5) Calcium petroleum sulfonate (A) and calcium salt of an octyl phenol-formaldehyde condensation product (B) (molecular weight=476 times one-half the number of phenol rings in the octyl phenol-formaldehyde condensation product) d. Benzene solutions of two compounds which meet all of the requirements of Additive A and Additive B, respectively, except that one or both of such compounds have molecular weights less than 200, for example, calcium diisopropyl salicylate (A) and tricthanol amine (B) (molecular weight of which=l49, and specific conductivity of solution of 1 gram of which per liter of benzene=9.1 10" ohm cm.-

e. Solutions of two components which meet all of the requirements of Additive A and Additive B, respectively, in volatile organic liquids which have an average of no more than 15 carbon atoms, but which have dielectric constants greater than 9, such as mixtures of benzene and nitrobcnzene wherein the concentration of nitrobenzene is greater than about 30 to 40 percent by volume. (Compare with items 43 through 46 of the table.)

Although the Additives A and B, as defined herein, are the only essential additives in the compositions of the present invention for the purposes set forth, other additivcs, such as dry cleaning assistants, oxidation inhibitors, corrosion inhibitors, and the like can also be added without detracting from the aforementioned advantages of such compositions.

This application is a continuation in part of our copending application, Serial No. 400,104, filed December 23, 1953, now abandoned.

We claim as our invention:

1. A volatile petroleum hydrocarbon liquid containing substantially only compounds having up to 12 carbon atoms per molecule, having a dielectric constant at 20 C. of less than 7, and containing from about 1 10"" to l gram mole per liter of said hydrocarbon liquid, each of a salt (A) of the group consisting of calcium diisopropyl salicylate and chromium diisopropyl salicylate and a salt (B) of the group consisting of sodium petroleum sulfonate, tetraisoamyl ammonium picrate and a salt of sulfonated dioctyl ester of succinic acid, containing only ions differing from those of chromium diisopropyl salicylate and from those of calcium diisopropyl silicylate.

2. A volatile petroleum hydrocarbon liquid containing substantially only compounds having up to 12 carbon atoms per molecule, having a dielectric constant at 20 C. of less than 7, and containing from about 1X10 to about 1X10' gram mole, per liter of said hydrocarbon liquid, each of calcium diisopropyl salicylate and sodium petroleum sulfonate.

3. A volatile petroleum hydrocarbon liquid containing substantially only compounds having up to 12 carbon atoms per molecule, having a dielectric constant at 20 C. of less than 7, and containing from about 1X10 to about 1 10- gram mole, per liter of said hydrocarbon liquid, each of chromium diisopropyl salicylate and sodium dioctyl sulfosuccinate.

4. A volatile petroleum hydrocarbon liquid containing substantially only compounds having up to 12 carbon atoms per molecule, having a dielectric constant at 20 C. of less than 7, and containing from about 1X10 to about 1x10- gram mole, per liter of said hydrocarbon liquid, each of chromium diisopropyl salicylate and lithium dioctyl sulfosuccinate.

5. A volatile petroleum hydrocarbon liquid containing substantially only compounds having up to 12 carbon atoms per molecule, having a dielectric constant at 20 C. of less than 7, and containing from about 1x10- to about l 10- gram mole, per liter of said hydrocarbon liquid, each of calcium diisopropyl salicylate and tetraisoamyl ammonium picrate.

6. A volatile petroleum hydrocarbon liquid containing substantially only compounds having up to 12 carbon atoms, having a dielectric constant at 20 C. of less than 7, and containing from about 1 10- to about 1 10 4 gram mole, per liter, of a chromium alkyl salicylate, and from about 1 10- to about 1 10 gram mole, per liter, of a salt of sulfonated dioctyl ester of succinic acid, containing only ions differing from those of said chromium alkyl salicylate.

References Cited in the file of this patent UNITED STATES PATENTS 2,326,182 Flett Aug. 17, 1943 2,503,744 Kenney et al. Apr. 11, 1950 2,639,227 Glendenning et a1 May 19, 1953 2,684,292 Caron et a1. July 20, 1954 2,696,453 Sanders et a1. Dec. 7, 1954 2,697,033 Ambrose et a1. Dec. 14, 1954 2,710,842 Heisig et al June 14, 1955 OTHER REFERENCES Industrial Solvents, Mellan, pp. 156, 173, 179, 186, Reinhold Publ. Corp, NY. (1939). 

1. A VOLATILE PETROLEUM HYDROCARBON LIQUID CONTAINING SUBSTANTIALLY ONLY COMPOUNDS HAVING UP TO 12 CARBON ATOMS PER MOLECULE, HAVING A DIELECTRIC CONSTANT AT 20* C. OF LESS THAN 7, AND CONTAINING FROM ABOUT 1X10-7 TO 1X10-4 GRAM MOLE PER LITER OF SAID HYDROCARBON LIQUID, EACH OF A SALT (A) OF THE GROUP CONSISTING OF CALCIUM DIISOPROPYL SALICYLATE AND CHROMIUM DIISOPROPYL SALICYLATE AND A SALT (B) OF THE GROUP CONSISTING OF SODIUM PETROLEUM SULFONATE, TETRAISOAMYL AMMONIUM PICRATE AND A SALT OF SULFONATED DIOCTYL ESTER OF SUCCINIC ACID, CONTAINING ONLY IONS DIFFERING FROM THOSE OF CHROMIUM DIISOPOPYL SALICYLATE AND FROM THOSE OF CALCIUM DIISOPROPYL SILICYLATE. 